Realization of Universal Ion-Trap Quantum Computation with Decoherence-Free Qubits

Monz, Thomas; Kim, K.; Villar, A. S.; Schindler, Philipp; Chwalla, M.; Riebe, M.; Roos, C. F.; Häffner, Hartmut; Hänsel, Wolfgang; Hennrich, Markus; Blatt, R.

doi:10.1103/physrevlett.103.200503

Cited by 93 publications

(107 citation statements)

References 32 publications

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“…(10). Since the reparametrized time remains infinite in the limit T → ∞, optimality of our solution is not affected by changing the unit of time.…”

Section: B Recovery Of Stirapmentioning

confidence: 99%

“…The condition for a dark state ensuring STIRAP turns out to be equivalent to the condition for a decoherence-free subspace to exist [9]. While in principle it is possible to construct quantum gates that preserve the structure of the decoherence free subspace [10], these gates are generally difficult to implement in practice for the following reason: the gate operations need to be carried out with controls that act on the physical qubits and this introduces couplings to the decohering subspaces [11]. This raises the question of whether losses can still be avoided if the controls are chosen in an optimal way.…”

Section: Introductionmentioning

confidence: 99%

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Controllability on relaxation-free subspaces: On the relationship between adiabatic population transfer and optimal control

et al. 2012

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We consider the optimal control problem of transferring population between states of a quantum system where the coupling proceeds only via intermediate states that are subject to decay. We pose the question whether it is generally possible to carry out this transfer. For a single intermediate decaying state, we recover the Stimulated Raman Adiabatic Passage (STIRAP) process which we identify as the global optimum in the limit of infinite control time. We also present analytical solutions for the case of transfer that has to proceed via two consecutive intermediate decaying states. We show that in this case, for finite power the optimal control does not approach perfect state transfer even in the infinite time limit. We generalize our findings to characterize the topologies of paths that can be achieved by coherent control under the assumption of finite power. If two or more consecutive states in an N -level chain are subject to decay, complete population transfer with finite-power controls is not possible.

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“…(10). Since the reparametrized time remains infinite in the limit T → ∞, optimality of our solution is not affected by changing the unit of time.…”

Section: B Recovery Of Stirapmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controllability on relaxation-free subspaces: On the relationship between adiabatic population transfer and optimal control

et al. 2012

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“…In the context of quantum information, two or more physical qubits, carried for example by atoms, can be used to encode one logical qubit that is decoherence-free [120]. Decoherence-free subspaces have been demonstrated, for example, in liquid-state nuclear magnetic resonance [121] and with trapped ions [122]. Numerical methods can be employed to identify (approximate) decoherence-free subspaces [123] and to find an external control that drives the system dynamics into a decoherence-free subspace [124].…”

Section: B Control Strategies For Open Quantum Systemsmentioning

confidence: 99%

Controlling open quantum systems: tools, achievements, and limitations

Koch

2016

J. Phys.: Condens. Matter

250

222

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The advent of quantum devices, which exploit the two essential elements of quantum physics, coherence and entanglement, has sparked renewed interest in the control of open quantum systems. Successful implementations face the challenge to preserve the relevant nonclassical features at the level of device operation. A major obstacle is decoherence which is caused by interaction with the environment. Optimal control theory is a tool that can be used to identify control strategies in the presence of decoherence. We review here recent advances in optimal control methodology that allow for tackling typical tasks in device operation for open quantum systems and discuss examples of relaxation-optimized dynamics. Optimal control theory is also a useful tool to exploit the environment for control. We discuss examples and point out possible future extensions.

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“…(6), provide additional flexibility in engineering the simulating Hamiltonian parameters. In contrast to the digital fashion of quantum simulation in decoherence free subspace [42], the present analog quantum simulation will save precious time in case of simu- …”

mentioning

confidence: 99%

Proposal for High-Fidelity Quantum Simulation Using a Hybrid Dressed State

et al. 2015

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A fundamental goal of quantum technologies concerns the exploitation of quantum coherent dynamics for the realisation of novel quantum applications such as quantum computing, quantum simulation, and quantum metrology. A key challenge on the way towards these goals remains the protection of quantum coherent dynamics from environmental noise. Here, we propose a concept of hybrid dressed state from a pair of continuously driven systems. It allows sufficiently strong driving fields to suppress the effect of environmental noise, while at the same time being insusceptible to both the amplitude and phase noise in the continuous driving fields. This combination of robust features significantly enhances coherence times under realistic conditions, and at the same time provides new flexibility in Hamiltonian engineering that otherwise is not achievable. We demonstrate theoretically applications of our scheme for noise resistant analog quantum simulation in the well studied physical systems of nitrogen-vacancy centers in diamond and of trapped ions. The scheme may also be exploited for quantum computation and quantum metrology. [11,12] to name just a few. This motivates the considerable effort that is being invested in the creation of the technological basis for these devices with the ultimate goal of constructing quantum devices that can outperform their classical counterparts. One of the main obstacles on this path is the effect of noise and decoherence due to interaction with an uncontrolled environment, the effect of which becomes increasingly severe as the number of system components grows. This poses a considerable challenge for achieving the quantum control of such systems while maintaining the quantum coherence of the system. Hence noise control is central for the future development of scalable quantum technologies.Various theoretical concepts and proposals, e.g. quantum error correction [13,14], decoherence free subspace [15][16][17][18][19][20][21], and dynamical decoupling [22][23][24][25][26][27][28][29][30][31], have been developed for the suppression or avoidance of quantum decoherence. Each of these methods are best suited for specific scenarios. For example, the decoherence free subspace approach is mainly useful in those cases in which noise exhibits a symmetry [21], which however is not always the case. One important example among others that suffer from non-collective noise is the nitrogen-vacancy (NV) center in diamond [32] as a promising physical system for quantum information processing and quantum sensing, the noise of which is dominated by the local nuclear and paramagnetic environment. These noise sources exhibit relatively long memory times and thus can be suppressed using continuous driving. This approach however suffers drawbacks for strong driving where intensity and phase fluctuations may become significant [31]. It is an important observation, that for decoupling fields that are derived from the same source, these fluctuations will be strongly corre-

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Realization of Universal Ion-Trap Quantum Computation with Decoherence-Free Qubits

Cited by 93 publications

References 32 publications

Controllability on relaxation-free subspaces: On the relationship between adiabatic population transfer and optimal control

Controllability on relaxation-free subspaces: On the relationship between adiabatic population transfer and optimal control

Controlling open quantum systems: tools, achievements, and limitations

Proposal for High-Fidelity Quantum Simulation Using a Hybrid Dressed State

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